FIG. 1 illustrates one embodiment of a plasma gun 100 used to process powder material. The plasma gun 100 is a DC plasma torch including a male electrode 120 and a female electrode 130. A power supply (not shown) is connected to the male electrode 120 and the female electrode 130 and delivers power through the plasma gun 100 by passing current across the gap 160 between the male electrode 120 and the female electrode 130. Furthermore, the plasma gun 100 includes a gas inlet 140 fluidly coupled to the gap 160 and configured to receive a working gas. The plasma gun 100 also includes a plasma outlet 150 fluidly coupled to the gap 160 on the opposite side of the plasma gun 100 from the gas inlet 140 and configured to provide a path through which a plasma stream 180 can be expelled from the plasma gun 100.
During operation, working gas flows through the gas inlet 140, through the gap 160 and out of the outlet 150. At the same time, power is supplied to the plasma gun 100. The current arcing across the gap 160 energizes the working gas and forms plasma 180, which flows out of the outlet 150. Powdered material 110 is fed into the plasma stream 180 through a channel 170 that is fluidly coupled to the pathway between the gap 160 and the plasma outlet 150 via a port 175 to the pathway. The plasma stream 180 entrains and works on the powder, forming a plasma powder mixture that flows out of the plasma gun 100 through the outlet 150.
There is a problem with this configuration of the plasma gun. The radiant and conductive heat of the plasma 180 melts the powder particles 110 before they get all the way down the channel 170 and exit the port 175 into the pathway between the gap 160 and the outlet 150. As a result, the melted particles agglomerate and stick to the sides of the channel 170 and the port 175, clogging them up. Consequently, operation of the plasma gun has to be stopped until it is cleaned, which results in a significant loss of productivity.